Applicant's DE 102 61 513 A1 (which corresponds to U.S. Pat. No. 7,134,733) describes a method of the general type under consideration in which a deceleration setpoint value is compared to a deceleration actual value and a current brake-application energy reference value Kappa is ascertained from this comparison. In general the driver command, which is derived from a brake pedal actuation of the driver, is taken as the deceleration setpoint value.
Furthermore, in general, the EBS of the tractor vehicle ascertains the axle load distribution ALD of the tractor vehicle from the differential slip control function DSC during braking from the rotational behavior of the front wheels and the rear wheels. ALD is the axle load distribution of the tractor vehicle front axle to the tractor vehicle rear axle and changes with the weight or the loading state of the tractor vehicle and therefore also with the loading state of the semitrailer truck combination.
Brake-application energy levels (also called setpoint pressure brake levels), which, have the unit bar/g, ate then ascertained separately for the tractor vehicle and the trailer vehicle from the brake-application energy level reference value Kappa and/or the axle load distribution ALD of the tractor vehicle.
In determining these separate brake-application energy levels for the tractor vehicle and the trailer vehicle, characteristic maps are used, which illustrate the dependencies of the brake-application energy levels of the tractor vehicle and of the trailer vehicle on at least one of the following variables: brake-application energy reference value Kappa and axle load distribution ALD of the tractor vehicle. In particular, coupling force control factors (also called influencing factors or CFC factors) are set in this case, which establish to what extent control of the coupling force between the tractor vehicle and the trailer vehicle occurs.
Fundamentally, the method described in DE 102 61 513 A1 represents a coupling force control method (also called CFC). The coupling force control method ascertains separate brake-application energy levels for the tractor vehicle and for the trailer vehicle. The CFC factor can be set to a value between 0 and 1 or 0% and 100%, wherein setting to 0 or 0% represents one extreme of a coupling force control and setting to 1 or 100% represents the other extreme.
Setting the CFC factor to 0 or 0% results in a coupling force control in which the ascertained separate brake-application energy levels for the partial vehicles of the vehicle combination are only dependent on the brake-application energy reference value Kappa. Setting the CFC factor to 1 or 100% results in a coupling force control in which the ascertained brake-application energy levels of the partial vehicles are dependent on the brake-application energy reference value Kappa and on the axle load distribution ALD. If a CFC factor is set to be greater than 0 or 0% and less than 1 or 100%, a coupling force control is carried out that has components of both coupling force control variants.
If the CFC factor is set to 1 or 100%, the control target of the coupling force control thus selected is 100% equal adhesion or adhesion ratios of the wheels of the tractor vehicle to the roadway and the wheels of the trailer vehicle to the roadway and therefore a coupling force between the partial vehicles of the vehicle combination of zero. The control target of this coupling force control variant follows the specification that each partial vehicle of the vehicle combination has to brake itself.
If the CFC factor is set to 0 or 0%, the control target of the coupling force control thus selected is a more equalized temperature level of the brakes of the tractor vehicle and the brakes of the trailer vehicle and also a reduction of the absolute peak temperatures, which occur during braking, of individual brakes of the wheels of the partial vehicles of the vehicle combination and therefore, in turn, an absolute lesser and more equalized brake lining wear behavior of the brake linings of all brakes of the partial vehicles of the vehicle combination; while dispensing with a coupling force between the partial vehicles of zero.
In the case of setting the CFC factor to 1 or 100%, a control target of equal adhesion ratios between wheels and roadway of the tractor vehicle and the trailer vehicle is sought; the coupling force or the forces transmitted between the vehicles during braking are therefore to be minimal or equal to zero, or such a control is sought. This can result in a different amount of wear on the brake linings and the tires of the tractor vehicle and the trailer vehicle.
At a CFC factor of 0 or 0%, in the event of a loading change (mass change) of the vehicle combination, the change of the braking work to be performed, which is caused by the load change, is distributed approximately uniformly to both partial vehicles. A more equalized wear behavior of the brake linings and the vehicle tires is sought in fills case, wherein a coupling force between the partial vehicles not equal to zero is accepted, i.e., control no longer occurs maximally for equal adhesion ratios of wheels to roadway of the wheels of the tractor vehicle and of the trailer vehicle.
The coupling force control factor can therefore primarily be selected freely, and determines the ratio of the braking work shares to be performed during braking, which are to be provided by the tractor vehicle and the trailer vehicle.
Systems and methods of the general type under consideration also allow the use of trailer vehicles, in particular semitrailers of a semitrailer vehicle combination, that do not have separate automatic load-dependent brake force control (ALB). This brake force control or ALB or ALB function can therefore also be implemented by the BBS of the tractor vehicle. However, unstable driving states can occur in such systems if extreme CFC factors are used in urgent extreme situations.